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3.1 Volcano and Plate Tectonics

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Vocabulary

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volcano- a weak part of earth's crust where magma comes out of
magma- is a mixture of rock-forming substances, gases, and water
lava- when magma comes out of the volcano
ring of fire- a volcanic belt
island arc- when a volcano makes a island
hot spot- when magma in the mantle melts through the crust

Outline

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What is a Volcano?

• a volcano is a weak spot in the crust where magma comes to the surface
  • magma is a molten mixture of rock-forming substances, gases, and water from the mantle
  • when magma comes to the surface, it's called lava
  • after the lava cools, it hardens to become solid rock

Locations of Volcanoes

• volcanoes occur in belts, or chains
  • one major volcanic belt is the Ring of Fire
    • most volcanoes occur along diverging plate boundaries, or in subduction zones around the edges of oceans

Volcanoes at Diverging Plate Boundaries

• volcanoes form along the mid-ocean ridge
  • only in a few places, as in Iceland and the Azores Islands, do the volcanoes of the mid-ocean ridge rise above the ocean's surface

Volcanoes at Converging Boundaries

• many volcanoes occur on islands, near boundaries where two plates collide
• the resulting volcanoes create a string of islands called an island arc

Hot Spot Volcanoes

• a hot spot is an area where magma from deep within the mantle melts through the crust
  • hot spots often lie in the middle of continental or oceanic plates far from any plate boundaries
  • hot spots can also form under continents